This invention pertains to a composition designed for use in dyeing human hair. While various forms of such dyeing compositions are known, a category of particular importance involves those containing a metal salt and a sulfur-containing reducing compound in an aqueous vehicle. Depending, in particular, upon the nature of the metal salt, these compositions may be employed to impart a variety of colors to human hair.
A class of metal salts which has proven particularly desirable is salts containing bismuth. Unfortunately, however, bismuth salts which are useful in such hair dyeing compositions have not proven readily susceptible to formulation.
This lack of success is formulating bismuth-containing hair dyeing compositions is partly a function of the limited number of known and active bismuth compounds which are soluble in conventional hair dyeing vehicles, particularly water. In addition, it is attributed to the low stability usually evidenced by bismuth salts in the presence of sulfur-containing reducing compounds. As a consequence, the use of bismuth salts for dyeing hair has been greatly limited.
In U.S. Pat. Nos. 1,937,365 and 2,719,104, there are described dyeing compositions utilizing inorganic salts of bismuth. These patents, however, require a number of different auxillary agents and indicated wide differences in coloration--viz. blond, red and brown--dependent upon these ingredients. Also, they are generally very unstable and so difficult to employ.
In U.S. Pat. No. 3,954,393, of Lapidus, there is disclosed another means by which useful hair dyeing compositions containing a bismuth salt may be obtained. There, an aqueous formulation including bismuth citrate solubilized by triethanolamine is described. That formulation yields various hair shades of brown. The scope of that invention is, however, limited. Consequently, many bismuth compounds remain unused.